Remotely operated bypass for a suspension damper

ABSTRACT

A damper assembly with a bypass for a vehicle comprises a pressure cylinder with a piston and piston rod for limiting the flow rate of damping fluid as it passes from a first to a second side of said piston. A bypass provides fluid pathway between the first and second sides of the piston separately from the flow rate limitation. In one aspect, the bypass is remotely controllable from a passenger compartment of the vehicle. In another aspect, the bypass is remotely controllable based upon one or more variable parameters associated with the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 61/143,152, filed Jan. 7, 2009, which is herein incorporated byreference.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention generally relate to a damperassembly for a vehicle. More specifically, the invention relates to aremotely operated bypass device used in conjunction with a vehicledamper.

Vehicle suspension systems typically include a spring component orcomponents and a dampening component or components. Typically,mechanical springs, like helical springs are used with some type ofviscous fluid-based dampening mechanism and the two are mountedfunctionally in parallel.

SUMMARY OF THE INVENTION

The present invention generally comprises a damper assembly having abypass. In one aspect, the assembly comprises a cylinder with a pistonand piston rod for limiting the flow rate of damping fluid as it passesfrom a first to a second portion of said cylinder. A bypass providesfluid pathway between the first and second portions of the cylinder andmay be independent of, or in conjunction with, the aforementioned flowrate limitation. In one aspect, the bypass is remotely controllable froma passenger compartment of the vehicle, In another aspect, the bypass isremotely controllable based upon one or more variable parametersassociated with the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features can be understoodin detail, a more particular description may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a section view showing a suspension damping unit with aremotely operable bypass, the bypass in a closed position.

FIG. 2 is a section view showing the suspension damping unit of FIG. 1with the bypass in an open position.

FIG. 3 is a schematic diagram showing a control arrangement for aremotely operated bypass.

FIG. 4 is a schematic diagram showing another control arrangement for aremotely operated bypass.

FIG. 5 is a graph showing possible operational characteristics of thearrangement of FIG. 4.

DETAILED DESCRIPTION

As used herein, the terms “down” “up” “downward” upward” “lower” “upper”and other directional references are relative and are used for referenceonly. FIGS. 1 and 2 are section views of a suspension damping unit 100.The damper includes a cylinder portion 102 with a rod 107 and a piston105. Typically, the fluid meters, from one side to the other side ofpiston 105, by passing through flow paths 110, 112 formed in the piston105. In the embodiment shown, shims 115, 116 are used to partiallyobstruct the flow paths 110, 112 in each direction. By selecting shims115, 116 having certain desired stiffness characteristics, the dampeningeffects can be increased or decreased and dampening rates can bedifferent between the compression and rebound strokes of the piston 105.For example, shims 115 are configured to meter rebound flow from therebound portion 103 of the cylinder 102 to the compression portion 104of the cylinder 102. Shims 116, on the other hand, are configured tometer compression flow from the compression portion of the cylinder tothe rebound portion. In one embodiment, shims 116 are not included onthe rebound portion side leaving the piston essentially “locked out” inthe compression stroke without some means of flow bypass. Note thatpiston apertures (not shown) may be included in planes other than thoseshown (e.g. other than apertures used by paths 110 and 112) and furtherthat such apertures may, or may not, be subject to the shims 115, 116 asshown (because for example, the shims 115, 116 may be clover-shaped orhave some other non-circular shape).

A reservoir 125 is in fluid communication with the damper cylinder 102for receiving and supplying damping fluid as the piston rod 107 moves inand out of the cylinder. The reservoir includes a cylinder portion 128in fluid communication with the damper cylinder 102. The reservoir alsoincludes a floating piston 130 with a volume of gas on a backside(“blind end” side) of it, the gas being compressible as the reservoircylinder 128 fills with fluid due to movement of the damper rod 107 andpiston 105 into the damper cylinder 102. Certain features of reservoirtype dampers are shown and described in U.S. Pat. No. 7,374,028, whichis incorporated herein, in its entirety, by reference. The upper portionof the rod 107 is supplied with a bushing set 109 for connecting to aportion of a vehicle wheel suspension linkage. In another embodiment,not shown, the upper portion of the rod 107 (opposite the piston) may besupplied with an eyelet to be mounted to one part of the vehicle, whilethe lower part of the housing shown with an eyelet 108 is attached toanother portion of the vehicle, such as the frame, that movesindependently of the first part. A spring member (not shown) is usuallymounted to act between the same portions of the vehicle as the damper.As the rod 107 and piston 105 move into cylinder 102 (duringcompression), the damping fluid slows the movement of the two portionsof the vehicle relative to each other due to the incompressible fluidmoving through the shimmed paths 110, 112 (past shims 116) provided inthe piston 105 and or through the metered bypass 150, as will bedescribed herein. As the rod 107 and piston 105 move out of the cylinder102 (during extension or “rebound”) fluid meters again through shimmedpaths 110 and 112 and the flow rate and corresponding rebound rate iscontrolled by the shims 115.

In one embodiment as shown in the Figures, a bypass assembly 150 isdesigned to permit damping fluid to travel from a first side of thepiston to the other side without traversing shimmed flow paths 110, 112that may otherwise be traversed in a compression stroke of the damper.In FIG. 1, the bypass 150 is shown in a closed position (e.g. a valve170 obstructs fluid passage through entry way 160) and in FIG. 2 thebypass is shown in an open position (e.g. valve 170 is open and fluidmay flow through passage 160). In FIG. 2, the piston is shown movingdownward in a compression stroke, the movement shown by arrow 157. Thebypass includes a cylindrical body 155 that communicates with the dampercylinder 102 through entry 160 and exit 165 pathways. In FIG. 2, withthe bypass open, the flow of fluid through the bypass is shown by arrow156. In one embodiment an entry valve 170 is located at the entrypathway 160 with a valve member 175 sealingly disposed and axiallymovable within the valve body. A needle-type check valve 180, allowingflow in direction 156 and checking flow in the opposite direction, islocated proximate exit pathway 165. The needle valve sets flowresistance through the bypass 150 during compression and restricts fluidfrom entering the bypass cylinder 150 during a rebound stroke of thedamper piston 105. In one embodiment the needle valve 180 is springloaded and biased closed. The initial compression force of the biasingspring 182 is adjusted via adjuster 183 thereby allowing a user topreset the needle valve opening pressure and hence the compressiondamping fluid flow rate (hence damping rate) through the bypass. Thebiasing force of the needle valve spring 182 is overcome by fluidpressure in the cylinder 155 causing the needle valve 180 to open duringa compression stroke.

The entry pathway 160 and entry valve 170 in the embodiments shown inFIGS. 1 and 2, are located towards a lower end of the damper cylinder102. In one embodiment, as selected by design, the bypass will notoperate after the piston 105 passes the entry pathway 160 near the endof a compression stroke. This “position sensitive” feature ensuresincreased dampening will be in effect near the end of the compressionstoke to help prevent the piston from approaching a “bottomed out”position (e.g. impact) in the cylinder 102. In some instances, multiplebypasses are used with a single damper and the entry pathways for eachmay be staggered axially along the length of the damper cylinder inorder to provide an ever-increasing amount of dampening (and lessbypass) as the piston moves through its compression stroke and towardsthe bottom of the damping cylinder. Certain bypass damper features aredescribed and shown in U.S. Pat. Nos. 6,296,092 and 6,415,895, each ofwhich are incorporated herein, in its entirety, by reference.

In one embodiment the bypass 150, as shown in FIGS. 1 and 2, includes afluid (e.g. hydraulic or pneumatic) fitting 201 disposed at an end ofthe entry valve body 170. The fluid fitting 201 is intended to carry acontrol signal in the form of fluid pressure to the valve member 175 inorder to move the valve 170 from an open to a closed position. In oneembodiment, valve member 175 is biased open by an annular spring 171located between an upper end of the valve member 175 and the lower axialend face of tube 155.

In one example, the valve 170 is moved to a closed position and thebypass feature disabled by remote control from a simpleoperator-actuated switch located in the passenger compartment of thevehicle. In one embodiment, fluid pressure for controlling (e.g.closing) the valve 170 is provided by the vehicle's own source ofpressurized hydraulic fluid created by, for example, the vehicle powersteering system. In one embodiment, pneumatic pressure is used tocontrol (e.g. close) the valve 170 where the pneumatic pressure isgenerated by an on-board compressor and accumulator system and conductedto the valve 170 via a fluid conduit. In one embodiment, a linearelectric motor (e.g. solenoid), or other suitable electric actuator, isused to move valve member 175 axially within valve body. A shaft of theelectric actuator (not shown) may be fixed to the valve member 175 suchthat axial movement of the shaft causes axial movement of the valvemember 175. In one embodiment, the electric actuator is configured to“push” the valve member 175 to a closed position and to “pull” the valvemember 175 to an open position depending on the direction of the currentswitched through the actuator. In one embodiment, the valve 170 isspring biased, for example, to an open position as previously describedherein, and the actuator, being switched by a potentiometer or othersuitable current or voltage modulator, moves the valve member 175against the biasing spring to a closed position or to some position ofdesired partial closure (depending on the operation of the switch). Suchpartial closure increases the compression stiffness of the damper butdoes not provide the more rigid dampening of complete bypass closure. Insuch electrical embodiments, the solenoid is wired (e.g. via electricalconduit) into the vehicle electrical system and switched to move thevalve 170 as described herein.

FIG. 3 is a schematic diagram illustrating a sample circuit 400 used toprovide remote control of a bypass valve using a vehicle's powersteering fluid (although any suitable fluid pressure source may besubstituted for reservoir 410 as could an electrical current source inthe case of an electrically actuated valve member 175). As illustrated,a fluid pathway 405 having a switch-operated valve 402 therein runs froma fluid (or current) reservoir 410 that is kept pressurized by, in oneembodiment, a power steering pump (not shown) to a bypass valve 170 thatis operable, for example, by a user selectable dash board switch 415.The valve 402 permits fluid to travel to the bypass valve 170, therebyurging it to a closed position. When the switch 415 is in the “off”position, working pressure within the damper, and/or a biasing membersuch as a spring 171 (as described herein in relation to FIGS. 1 & 2) orannular atmospheric chamber (not shown), returns the bypass to itsnormally-open position. Hydraulically actuated valving for use withadditional components is shown and described in U.S. Pat. No. 6,073,536and that patent is incorporated by reference herein in its entirety.While FIG. 3 is simplified and involves control of a single bypassvalve, it will be understood that the valve 402 could be plumbed tosimultaneously provide a signal to two or more bypass valves operablewith two or more vehicle dampers and or with a single damper havingmultiple bypass channels and multiple corresponding valves (e.g. 175).Additional switches could permit individual operation of separate damperbypass valves in individual bypass channels, whether on separate dampersor on the same multiple bypass damper, depending upon an operator'sneeds. While the example of FIG. 3 uses fluid power for operating thebypass valve, a variety of means are available for remotely controllinga valve. For instance, a source of electrical power from a 12 voltbattery could be used to operate a solenoid member, thereby shiftingvalve member 175 in bypass valve 170 between open and closed positions.The signal can be either via a physical conductor or an RF signal (orother wireless such as Bluetooth, WiFi, ANT) from a transmitter operatedby the switch 415 to a receiver operable on the bypass valve 175.

A remotely operable bypass like the one described above is particularlyuseful with an on/off road vehicle. These vehicles can have as much as20′ of shock absorber travel to permit them to negotiate rough, uneventerrain at speed with usable shock absorbing function. In off-roadapplications, compliant dampening is necessary as the vehicle relies onits long travel suspension when encountering off-road obstacles,Operating a vehicle with very compliant, long travel suspension on asmooth road at higher speeds can be problematic due to thespringiness/sponginess of the suspension. Such compliance can causereduced handling characteristics and even loss of control. Such controlissues can be pronounced when cornering at high speed as a compliant,long travel vehicle may tend to roll excessively. Similarly, such avehicle may pitch and yaw excessively during braking and acceleration.With the remotely operated bypass “lock out” described herein, dampeningcharacteristics of a shock absorber can be completely changed from acompliantly dampened “springy” arrangement to a highly dampened and“stiffer” system ideal for higher speeds on a smooth road. In oneembodiment where compression flow through the piston is completelyblocked, closure of the bypass 150 results in substantial “lock out” ofthe suspension (the suspension is rendered essentially rigid). In oneembodiment where some compression flow is allowed through the piston(e.g. ports 110, 112 and shims 116), closure of the bypass 150 resultsin a stiffer but still functional compression damper. In one embodiment,the needle valve 180 is tuned (using adjuster 183), and the shims 116sized, to optimize damping when the bypass 150 is open and when bypass150 is closed based on total anticipated driving conditions. In oneembodiment the needle valve adjuster 183 is connected to a rotaryelectrical actuator so that adjustment of the needle valve4 180 may beperformed remotely as disclosed herein referencing the bypass valve 170.

In addition to, or in lieu of, the simple, switch operated remotearrangement of FIG. 3, the remote bypass can be operated automaticallybased upon one or more driving conditions. FIG. 4 shows a schematicdiagram of a remote control system 500 based upon any or all of vehiclespeed, damper rod speed, and damper rod position. One embodiment of FIG.4 is designed to automatically increase dampening in a shock absorber inthe event a damper rod reaches a certain velocity in its travel towardsthe bottom end of a damper at a predetermined speed of the vehicle. Inone embodiment the system adds dampening (and control) in the event ofrapid operation (e.g. high rod velocity) of the damper to avoid abottoming out of the damper rod as well as a loss of control that canaccompany rapid compression of a shock absorber with a relative longamount of travel. In one embodiment the system adds dampening (e.g.closes or throttles down the bypass) in the event that the rod velocityin compression is relatively low, but the rod progresses past a certainpoint in the travel. Such configuration aids in stabilizing the vehicleagainst excessive low rate suspension movement events such as corneringroll, braking and acceleration yaw and pitch and “g-out.”

FIG. 4 illustrates, for example, a system including three variables: rodspeed, rod position and vehicle speed. Any or all of the variables shownmay be considered by processor 502 in controlling the valve 175. Anyother suitable vehicle operation variable may be used in addition to orin lieu of the variables 515, 505, 510 such as for example piton rodcompression strain, eyelet strain, vehicle mounted accelerometer data orany other suitable vehicle or component performance data. In oneembodiment, a suitable proximity sensor or linear coil transducer orother electro-magnetic transducer is incorporated in the dampeningcylinder to provide a sensor to monitor the position and/or speed of thepiston (and suitable magnetic tag) with respect to the cylinder. In oneembodiment, the magnetic transducer includes a waveguide and a magnet,such as a doughnut (toroidal) magnet that is joined to the cylinder andoriented such that the magnetic field generated by the magnet passesthrough the piston rod and the waveguide. Electric pulses are applied tothe waveguide from a pulse generator that provides a stream of electricpulses, each of which is also provided to a signal processing circuitfor timing purposes. When the electric pulse is applied to the waveguidea magnetic field is formed surrounding the waveguide. Interaction ofthis field with the magnetic field from the magnet causes a torsionalstrain wave pulse to be launched in the waveguide in both directionsaway from the magnet. A coil assembly and sensing tape is joined to thewaveguide. The strain wave causes a dynamic effect in the permeabilityof the sensing tape which is biased with a permanent magnetic field bythe magnet, The dynamic effect in the magnetic field of the coilassembly due to the strain wave pulse, results in an output signal fromthe coil assembly that is provided to the signal processing circuitalong signal lines. By comparing the time of application of a particularelectric pulse and a time of return of a sonic torsional strain wavepulse back along the waveguide, the signal processing circuit cancalculate a distance of the magnet from the coil assembly or therelative velocity between the waveguide and the magnet. The signalprocessing circuit provides an output signal, either digital or analog,proportional to the calculated distance and/or velocity. Such atransducer-operated arrangement for measuring rod speed and velocity isdescribed in U.S. Pat. No. 5,952,823 and that patent is incorporated byreference herein in its entirety.

While a transducer assembly located at the damper measures rod speed andlocation, a separate wheel speed transducer for sensing the rotationalspeed of a wheel about an axle includes housing fixed to the axle andcontaining therein, for example, two permanent magnets. In oneembodiment the magnets are arranged such that an elongated pole piececommonly abuts first surfaces of each of the magnets, such surfacesbeing of like polarity. Two inductive coils having flux-conductive coresaxially passing therethrough abut each of the magnets on second surfacesthereof, the second surfaces of the magnets again being of like polaritywith respect to each other and of opposite polarity with respect to thefirst surfaces. Wheel speed transducers are described in U.S. Pat. No.3,986,118 which is incorporated herein by reference in its entirety.

In one embodiment, as illustrated in FIG. 4, a logic unit 502 withuser-definable settings receives inputs from the rod speed 510 andlocation 505 transducers as well as the wheel speed transducer 515. Thelogic unit is user-programmable and depending on the needs of theoperator, the unit records the variables and then if certain criteriaare met, the logic circuit sends its own signal to the bypass to eitherclose or open (or optionally throttle) the bypass valve 175. Thereafter,the condition of the bypass valve is relayed back to the logic unit 502.

FIG. 5 is a graph that illustrates a possible operation of oneembodiment of the bypass assembly 500 of FIG. 4. The graph assumes aconstant vehicle speed. For a given vehicle speed, rod position is shownon a y axis and rod velocity is shown on an x axis. The graphillustrates the possible on/off conditions of the bypass at combinationsof relative rod position and relative rod velocity. For example, it maybe desired that the bypass is operable (bypass “on”) unless the rod isnear its compressed position and/or the rod velocity is relatively high(such as is exemplified in FIG. 5). The on/off configurations of FIG. 5are by way of example only and any other suitable on/off logic based onthe variable shown or other suitable variables may be used. In oneembodiment it is desirable that the damper become relatively stiff atrelatively low rod velocities and low rod compressive strain(corresponding for example to vehicle roll, pitch or yaw) but remainscompliant in other positions. In one embodiment the piston rod 107includes a “blow off” (overpressure relief valve typically allowingoverpressure flow from the compression side to the rebound side) valvepositioned in a channel coaxially disposed though the rod 107 andcommunicating one side of the piston (and cylinder) with the other sideof the piston (and cylinder) independently of the apertures 110,112 andthe bypass 150.

In one embodiment, the logic shown in FIG. 4 assumes a single damper butthe logic circuit is usable with any number of dampers or groups ofdampers. For instance, the dampers on one side of the vehicle can beacted upon while the vehicles other dampers remain unaffected.

While the examples illustrated relate to manual operation and automatedoperation based upon specific parameters, the remotely operated bypasscan be used in a variety of ways with many different driving and roadvariables. In one example, the bypass is controlled based upon vehiclespeed in conjunction with the angular location of the vehicle's steeringwheel. In this manner, by sensing the steering wheel turn severity(angle of rotation), additional dampening can be applied to one damperor one set of dampers on one side of the vehicle (suitable for exampleto mitigate cornering roll) in the event of a sharp turn at a relativelyhigh speed. In another example, a transducer, such as an accelerometermeasures other aspects of the vehicle's suspension system, like axleforce and/or moments applied to various parts of the vehicle, likesteering tie rods, and directs change to the bypass valve positioning inresponse thereto. In another example, the bypass can be controlled atleast in part by a pressure transducer measuring pressure in a vehicletire and adding dampening characteristics to some or all of the wheelsin the event of, for example, an increased or decreased pressurereading. In still another example, a parameter might include agyroscopic mechanism that monitors vehicle trajectory and identifies a“spin-out” or other loss of control condition and adds and/or reducesdampening to some or all of the vehicle's dampers in the event of a lossof control to help the operator of the vehicle to regain control.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A vehicle suspension damper comprising: a cylinder and a pistonassembly comprising a piston and piston rod; working fluid within saidcylinder; a passageway through said piston allowing and limiting a flowrate of the working fluid through the piston in at least one direction;a bypass having fluid pathway between the first and second sides of thepiston; and a remotely controllable valve for limiting the flow of fluidthrough the bypass.